This invention relates to a seat belt buckle with a tilting latch.
In the Specification of U.S. Pat. No. 4,451,958 there is described a vehicle seat safety belt buckle with a locking element formed of a metal plate with a pair of laterally extending tabs at one end thereof by means of which the plate is tiltably carried in openings in the sides of a U-shaped frame to permit movement of a projection into or out of an aperture in a tongue to be locked into the frame. A retaining member for the locking element is guided in L-shaped slots in the sides of the frame and is associated with an articulated rocker actuable by a tongue ejector. Moreover a slidable release button is provided with surfaces which cooperate in an unlocking sense with the locking element and can also assist in lifting the locking projection out of the tongue aperture. In this arrangement the retaining element is movable into its locking position by a rocking member which is pivotally actuated by a tongue ejector when the tongue is inserted and this rocking member at the same time changes the line of action of a compression spring to urge the locking element towards its locking position.
The buckle described above has some shortcomings in that it is not inertially immune to impulses such as may be caused by the action of a seat-belt pretensioner in crash conditions. Also locking of the element is dependent upon the aforementioned change of line of action of the compression spring, and the balance of the set of conditions to achieve this may be critical.
The present invention has the object of reducing the above shortcomings.
According to the present invention, there is provided a seat belt buckle comprising a generally U-shaped frame, presenting an opening at one end for receiving a tongue between two side portions and generally parallel to a base portion, said tongue being engageable with a spring loaded ejector, a locking element having means at one end engaging the side portions to be tiltable therebetween whereby a projection of said element is movable into or out of locking relationship with an aperture of said tongue and a retaining member movable into or out of a locking position wherein it prevents movement of the projection away from said locking relationship and said retaining member being movable by the action of a release member to permit release of the tongue characterised in that a spring loaded rocking member is pivotally located by said tiltable locking element so that the spring loading of said rocking member acts in a sense to urge the rocking member into a position to constrain the retaining member to said locking position thereof and the release member has means operable to move the rocking member against said spring loading and permit displacement of the retaining member from its locking position.
In accordance with a particular feature of the invention, the rocking member is inertially substantially balanced about its pivot point or preferably is inertially over-balanced in a sense to prevent any tendency to move out of its restraining position in relation to the restraining member under frontal crash conditions.
In order that the invention may be more clearly understood and readily carried into effect, the same will now be further described by way of an example with reference to the accompanying drawings.